The invention relates to a glow plug control device. Modern glow plug control devices generate an effective voltage for each glow plug from an on-board power supply voltage of a motor vehicle by means of pulse-width modulation. Glow plug control devices therefore contain a power transistor, with which the heating current is switched on and off and is thus pulse-width-modulated.
Glow plug control devices can control the temperature of a glow plug by adapting the duty cycle of the pulse-width-modulated effective voltage. A precise control of the fed power is necessary for precise temperature control. For a closed-loop control of the temperature, the present temperature of the glow plug is established from a resistance measurement. Both for open and closed-loop control a precise measurement of the intensity of the heating current is of great significance. Many modern glow plug control devices therefore contain a measuring resistor for measuring the strength of the heating current.
A constant objective when developing glow plug control devices is to bring a glow plug as quickly as possible to a desired temperature and to keep it there with great accuracy. Excessively high temperatures of a glow plug lead to the premature failure thereof. Too low temperatures lead to a sub-optimal combustion of the fuel.